During meiosis, homologous chromosomes seek each other out and are then tethered together by the synaptonemal complex (SC) and sister chromatid cohesion, without which homologous recombination and meiotic division cannot occur. Mice with mutations in genes encoding any of the SC components or cohesins show meiotic pairing defects and, in most cases, are sterile. The SC protein, FKBP6, which is essential for completion of meiotic prophase I in male mice, interacts with a novel meiotic kinase, NEK1 (NIMA-related kinase 1). NEK1 is a dual activity serine/threonine and tyrosine kinase, and is highly expressed in germ cells, particularly the narrow window encompassing the entry into, and progression through, Prophase I. Nek1 mutant mice show severe developmental defects, not only in their fertility, but also show growth defects, cranial-facial abnormalities and polycystic kidney disease. The central hypothesis of this proposal is that NEK1 is required for prophase I to metaphase progression, as it links key SC events with those involving sister chromatid cohesion. To test this hypothesis, I will analyze meiotic progression in a line of Nek1kat2J mice harboring a single nucleotide insertion and a subsequent premature stop, resulting in truncation of the protein product and a null phenotype. Two specific aims are proposed: (1) to perform an in-depth study of the relationship between FKBP6, NEK1 and cohesin proteins directly in mouse spermatocytes, and compare this directly with the action in oocytes, to determine any sexual dimorphism in the meiotic phenotype and (2) to assess the serine/threonine and tyrosine kinase activities of both the wild type and mutant forms of NEK1 directly in mouse germ cells. These experiments will provide novel and exciting data on the role of NEK1 in meiotic progression, as well as on the mechanisms of cohesin removal at the end of prophase I, a subject on which there is very little reported data. I approach this project with a strong background in both molecular biology and cytogenetics (with an emphasis on mammalian gametogenesis);my goal is to strengthen my proteomics skills in order to execute this project and move toward independent research. For four years I have been a postdoctoral researcher at Cornell University, two of these years funded by an HD foundation postdoctoral award. At Cornell I have conducted research in the laboratory of Dr. Paula Cohen, whose lab has been instrumental in documenting the major crossover pathways mouse meiosis. My immediate career goals include publishing in high-impact journals, establishing a science network outside of Cornell and to present research at academic institutions;my long-term career goal is to obtain a tenure-track position at a high caliber institution where I can focus on independent research as well as the training of future researchers. My progress in this direction will be assessed by regular meetings with my co-mentors, inter-departmental seminars on my research and, ultimately, by my publication record. PUBLIC HEALTH RELEVANCE: Infertility affects about 15% of the reproductive population of the United States, with many of the underlying causes being unknown. Errors during prophase I of meiosis can lead to fertility or birth defects in humans. Understanding the role of key genes involved in ensuring proper chromosomal segregation during meiosis will increase our understanding of the mechanisms controlling these events and the complex causes of infertility.